U.S. Pat. 5,718,741 (Hull et al.), which is assigned to the assignee of this application, the disclosure of which is incorporated herein by reference, discloses a forehearth for cooling a stream of molten glass as it flows from a glass melting furnace to a forming machine for forming the molten glass into finished products, for example, hollow glass containers of the type widely used in packaging various food, beverage and other products. In the arrangement of the '741 Patent, and in a variety of other types of forehearths, molten glass flows downwardly through an opening, or a plurality of openings, in the bottom of a feeder bowl at an end of the forehearth that is remote from the end into which molten glass from the melting furnace flows.
To control the flow of molten glass from a forehearth feeder bowl, a vertically extending, refractory feeder tube is provided with its lowermost end immersed in the feeder bowl to a level slightly above the inside surface of the bottom of the feeder bowl and surrounding the opening(s) at the bottom of the feeder bowl, and the ceramic tube is caused to rotate slowly during the operation of the forehearth to ensure a proper mixing and temperature uniformity of the molten glass flowing from the feeder bowl. A feeder bowl refractory tube with a tube drive system of this general type is disclosed in U.S. Pat. No. 5,660,610 (DiFrank), which is also assigned to the assignee of this application, the disclosure of which is also incorporated by reference herein. Other glass forehearth feeder bowl feeder tube arrangements are described in U.S. Pat. No. 5,693,114 (Scott), U.S. Pat. No. 4,514,209 (Mumford) and U.S. Pat. No. 4,478,631 (Mumford), the disclosure of each of which is also incorporated by reference herein.
From time to time during the operation of a glass manufacturing system of a type employing a forehearth feeder bowl feeder tube of the type described above it is necessary to remove the feeder tube and/or the feeder bowl for repair or replacement. In the case of the replacement of the feeder bowl, the feeder tube must also be swung horizontally out of the way of the feeder bowl as well as being lifted vertically so that its lower edge clears the upper extent of the feeder bowl. It is also necessary from time to time to be able to adjust the height of the feeder tube. As a feeder tube of this type is quite massive, very large forces are required to lift it from its operating position. Heretofore, counterweighted lift mechanisms were employed for this purpose, and these mechanisms typically employed gear boxes with considerable backlash, thus making precise positioning and motions of the feeder tube very difficult. Moreover, in these arrangements, precise adjustment of the position of the feeder tube in a horizontal plane, in X and/or Y directions, was difficult to achieve in that the horizontal motions of the counterweight lift mechanisms could not be isolated along X or Y axes. Further, counterweighted lift mechanisms are cumbersome because of the dead weights employed in them, and the vertical feeder tube slide supports are subject to wear during up and down tube adjustments, which can impart a wobbling motion to the tube support system and thereby lead to undesired glass gob weight variation in a feeder bowl used in conjunction with a glass container forming machine of the individual section (I.S.) type. Also, from time to time, it is necessary to replace a feeder bowl itself. In the prior art, this required removal of the entire feeder tube mechanism itself.